Tortuous path filter for airbag inflator

ABSTRACT

An airbag assembly may include an airbag and an inflator that provides inflation gas to inflate the airbag. A filter module may be positioned such that inflation gas exiting the inflator must first pass through the filter module. The filter module may be formed of a sheet of metal that is wrapped into a generally spiraling tubular shape. The filter module may have an inner layer, an intermediate layer, and an outer layer. The intermediate layer generally encircles the inner layer, and the outer layer generally encircles the inner layer and the intermediate layer in a spiraling fashion. The inner layer, the intermediate layer, and the outer layer each may have a pattern of holes and dimples that are separate from and/or displaced from each other. The dimples may protrude toward an adjacent layer to maintain spacing to enable relatively unrestricted gas flow from the holes of the inner layer through unaligned holes of the intermediate layer and the outer layer. The resulting tortuous gas flow path may help to slow, cool, and/or purify the gas before it exits the inflator.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. national stage of PCT Application No.PCT/US2017/047782 filed on Aug. 21, 2017, which claims priority to U.S.application Ser. No. 15/246,337 filed on Aug. 24, 2016, the entirecontent of each above-referenced application is incorporated herein bythis reference.

TECHNICAL FIELD

The present invention relates to automotive safety. More specifically,the present invention relates to airbag inflators that enhance thecost-effectiveness of airbag systems.

BACKGROUND

Inflatable safety restraint devices, or airbags, are mandatory on mostnew vehicles. Airbags are typically installed as part of a system withan airbag module in the steering wheel on the driver's side of car andin the dashboard on the passenger side of a car. In the event of anaccident, a sensor within the vehicle measures abnormal deceleration andtriggers the ignition of a charge contained within an inflator.Expanding gases from the charge fill the airbags, which immediatelyinflate in front of the driver and passenger to protect them fromharmful impact with the interior of the car. Typically, airbags areconcealed within the vehicle trim to be invisible during normal vehicleoperation. In addition to the driver's side and passenger's sideairbags, many vehicles also have other airbags such as side airbagsand/or inflatable curtains that inflate outboard of vehicle occupants toprovide side impact, rollover, ejection, and/or small overlap collisionprotection, knee airbags, inflatable harnesses, and the like.

The inflator is a critical part of the airbag assembly because itsupplies the inflation gas needed to inflate the airbag cushion.Typically, inflators are compressed gas, pyrotechnic, or hybridinflators. “Compressed gas” inflators contain gas under pressure, while“pyrotechnic” inflators contain a pyrotechnic gas generant that ignitesto produce the gas. “Hybrid” inflators typically use both compressed gasand a pyrotechnic charge. Some inflators are “dual stage,” meaning thatthey can receive two independent activation signals to enable productionof a selectively variable quantity of inflation gas, and others haveonly a single stage. However, single stage inflators can have multipletimed events, such as the ignition of multiple separate pyrotechniccharges and/or the release of distinct volumes of compressed gas, thatare all triggered by a single activation signal.

Inflators of all types are typically made from a wide variety of parts.Each inflator may contain a selection of chambers, diffusers, filters,frangible membranes, initiators, generants, baffles, and containers,attachment hardware, and other components. Each of these parts addssignificantly to the cost of the inflator. Hence, the inflator typicallymakes up a large portion of the cost of an airbag assembly.

Additionally, a series of different manufacturing steps may be needed tomanufacture each inflator. The quantity of steps involved not onlyfurther increases the cost of potential inflators, it also increases thelikelihood of defects in material or workmanship in the finishedinflator.

SUMMARY OF THE INVENTION

The various systems and methods of the present disclosure have beendeveloped in response to the present state of the art, and inparticular, in response to the problems and needs in the art that havenot yet been fully solved by currently available airbag systems andmethods. Thus, it is advantageous to provide airbag systems and methodsthat provide reliable protection for vehicle occupants in a wide varietyof collision situations. Further, it is advantageous to minimizemanufacturing and installation costs. The exemplary embodiments of thepresent disclosure may have other benefits that are not specifically setforth herein.

To achieve the foregoing, the exemplary embodiments broadly describedherein comprise an inflator that may be part of an airbag assembly forprotecting a vehicle occupant from injury. An inflator may comprise ahousing having a central longitudinal axis and may have one or morediffuser holes through which inflation gas is emitted to fill an airbag.Inflators typically have a gas source contained within a chamber definedwithin the housing. That gas source may be compressed gas, a pyrotechnicgas generant, or combination of compressed gas and generant. In responseto receipt ant activation signal, the gas source provides a gas.

In some embodiments, the inflator will have a filter or filter moduledesigned to slow gas flow, to cool the gas before entering the airbag,and to capture impurities within the gas. In the present disclosure,exemplary embodiments have a filter module comprising a unitary body(that may be made of a metal, such as steel) with an inner layerportion, an intermediate layer portion, and an outer layer portion thatis prepared and then formed into a rolled spiral of a generally tubularshape by wrapping around a correctly-sized mandrel or other means. Thefilter module is then positioned within the housing to surround acentral longitudinal axis. As rolled and positioned within the housingof the inflator, the filter module defines an inner layer, anintermediate layer, and an outer layer and maintains its shape withoutthe need for welding.

The inner layer comprises a first array of holes that, in someembodiments, are formed by perforation. The inflation gas is receivedinternal of the inner layer and passes through the first array of holesto reach the intermediate layer. The intermediate layer comprises asecond array of holes that may be formed by perforation. Each hole ofthe second array of holes does not align radially with the hole of thefirst array of holes nearest such hole of the second array of holes.This causes the inflation gas passing through the inner layer to changedirection and flow axially in search of an exit.

The intermediate layer is positioned such that the inflation gas passesthrough the second array of holes to reach the outer layer. The outerlayer comprises a third array of holes. Again, each hole of the secondarray of holes does not align radially with the hole of the third arrayof holes nearest such hole of the second array of holes. The inflationgas, this time passing through the intermediate layer, is once againforced to change direction and flow axially in search of an exit. Eachhole of the third array of holes does not align with any of the one ormore diffuser holes. Before the inflation gas can exit the inflatorthrough any of the diffuser holes, the inflation gas must changedirection again and travel axially in search of a diffuser hole throughwhich to exit.

Of course, it should be understood that there may be more than oneintermediate layer and that intermediate layers need not necessarilyhave the same array of holes.

The exemplary embodiments of the present disclosure have a filter modulewith a unitary body having a plurality of protrusions. At least oneprotrusion of the plurality of protrusions is disposed adjacent at leastone of the holes of the first array of holes of the inner layer and someembodiments may have one protrusion disposed adjacent each of the holesof the first array of holes of the inner layer. At least one otherprotrusion of the plurality of protrusions is disposed adjacent at leastone of the holes of the second array of holes of the intermediate layer.At least another protrusion of the plurality of protrusions is disposedadjacent at least one of the holes of the third array of holes of theouter layer. In some embodiments, each protrusion of the inner layerprotrudes toward the intermediate layer, each protrusion of theintermediate layer protrudes toward the outer layer, and each protrusionof the outer layer protrudes toward an interior wall of the housing. Theprotrusions are sized and shaped to maintain a gap between the innerlayer and the intermediate layer, between the intermediate layer and theouter layer, and between the outer layer and the interior wall of thehousing. This gap defines a spiraling plenum through which the inflationgas passes on a tortuous path from the gas source through the filtermodule to exit the inflator through the one or more diffuser holes.

It should be understood that the protrusions can take on many forms inmany sizes and shapes without departing from the spirit of theinvention. For example, the protrusions may be dimples that form a moundbut do not perforate the unitary body of the filter module, elongateddimples, ridges, or inclined flaps made by piercing the unitary body(forming holes in the form of slits) and bending the flaps on an inclineto reach a desired height. So long as the number of protrusions are ofsufficient number, size and height and dispersed sufficiently tomaintain the gap that defines the spiral plenum, protrusions serve theirfunction while strengthening the layers of the filter module. Of course,having more protrusions will dictate that the flow of inflation gas thatmust move around such protrusions take more tortuous paths to exit theinflator; however, the number, size, and distribution of the protrusionsand the holes may be adjusted and may be fine-tuned to optimize thedesired amount of flow restriction, the desired amount of cooling,and/or the desired amount of impurities captured for filling an airbagin the most material- and cost-effective way. Since the desired amountof flow restriction, the desired amount of cooling, and/or the desiredamount of impurities captured for filling an airbag is dependent uponthe size, shape, location, and the desired rate of deployment, thenumber, size, and distribution of the protrusions and the holes shouldbe adjusted and fine-tuned to optimize the effectiveness of the filtermodule.

In some embodiments, the holes of the first array of holes in the innerlayer are each larger than the holes of the second array of holes in theintermediate layer. By enlarging the holes in the first array of holesin the inner layer, unwanted erosion of the intermediate layer where thehot inflation gas jets straight through the holes of the first array ofholes against the inside wall of the intermediate layer is minimized.The size of the holes of the first array of holes may be enlarged untilerosion is no longer observed. Similarly, the holes of the second arrayof holes can also be enlarged to avoid erosion on the outer layer of thefilter module.

Additionally, a desired choking point in the flow of inflation gasthrough the inflator may be determined by adjusting the number and/orsize of the holes in the first array of holes, in the second array ofholes, and in the third array of holes, as well as the number and/orsize of the diffuser holes.

Prior to forming the unitary body of the filter module into a rolledspiral of generally tubular shape by forming around a correctly-sizedmandrel or other means, the unitary body is typically flat and has, insome embodiments, a length and a width of a rectangular shape. The firstarray of holes in the unitary body is arranged in a first grid such thateach hole in the first array of holes aligns longitudinally with atleast one other of the holes of the first array of holes and also alignslaterally with at least one differing hole of the first array of holes.In one exemplary embodiment, the first array of holes is arranged in afirst grid wherein each line of longitudinally aligned holes has thesame number of holes and each line of laterally aligned holes has thesame number of holes.

The second array of holes is arranged in a second grid such that eachhole in the second array of holes aligns longitudinally with at leastone other of the holes of the second array of holes and also alignslaterally with at least one differing hole of the second array of holes.However, the holes aligned longitudinally in the first array of holes donot align longitudinally with the holes aligned longitudinally in thesecond array of holes. This non-alignment causes the flow of inflationgas to divert and travel axially before passing through the second arrayof holes. In another exemplary embodiment, the second array of holes isarranged in a second grid wherein each line of longitudinally alignedholes has the same number of holes and each line of laterally alignedholes has the same number of holes.

The third array of holes arranged in a third grid such that each hole inthe third array of holes aligns longitudinally with at least one otherof the holes of the third array of holes and also aligns laterally withat least one differing hole of the third array of holes. The holesaligned longitudinally in the third array of holes do not alignlongitudinally with the holes aligned longitudinally in the second arrayof holes. This non-alignment causes the flow of inflation gas to divertand travel axially before passing through the third array of holes. Inyet another exemplary embodiment, the third array of holes is arrangedin a third grid wherein each line of longitudinally aligned holes hasthe same number of holes and each line of laterally aligned holes hasthe same number of holes.

In another exemplary embodiment, one or more of the first array ofholes, the second array of holes, and the third array of holes has astaggered array pattern. An exemplary staggered array pattern may havemultiple lines of longitudinally aligned holes wherein each hole of anyof the multiple lines of longitudinally aligned holes also alignslaterally with at least one hole of another of the multiple lines oflongitudinally aligned holes, but does not align laterally with any ofthe holes of at least one other of the multiple lines of longitudinallyaligned holes.

In some embodiments, the unitary body of the filter module is wider atthe outer layer than at the inner and intermediate layers. When wrappedinto a spiral, the outer layer is longer at one end than the inner andintermediate layers. More space is provided at that end because theinner diameter of the outer layer is larger than the inner diameter ofthe inner layer. For inflators with frangible burst disks disposedbetween the gas source and the filter module, the burst disk has alarger diameter opening capability than it would have had if the innerlayer abutted the burst disk. This wider configuration for the outerlayer enables the burst disk to open over the full, inner diameter ofthe outer layer. Other applications may require that the inner orintermediate layer(s) be wider that the other layers for variousreasons.

The exemplary embodiments of the present disclosure include a unitaryfilter module for insertion into an inflator for an airbag assembly.Inflators having an elongated housing with a central longitudinal axisare particularly suitable. Such inflators typically have at least onediffuser hole and a gas source contained within a chamber defined withinthe housing. In response to an activation signal, the gas sourceprovides a gas. Such inflators can use compressed gas, pyrotechnicgenerants, or a hybrid thereof. Such inflators also frequently havefilters to slow the gas flow, cool the gas, and filter out impurities.

The exemplary embodiments of the unitary filter module of the presentdisclosure have a flat mode used to pre-prep the unitary body of thefilter module for wrapping into a spiraling rolled configuration forinsertion into the housing of the inflator (herein referred to as an“inserted spiral rolled mode”). The unitary body has a length (alongitudinal direction) and a width (a lateral direction) and isgenerally divided into an inner layer portion, an intermediate layerportion, and an outer layer portion.

In the flat mode, the inner layer portion is prepared with a first arrayof holes arranged in a first grid. This first grid may have any of anumber of patterns, but one exemplary pattern of holes are arranged suchthat each hole in the first array of holes aligns longitudinally with atleast one other of the holes of the first array of holes and also alignslaterally with at least one differing hole of the first array of holes.The intermediate layer portion comprises a second array of holesarranged in a second grid. The second grid need not have the samenumber, pattern, or size of holes as the first array of holes. However,for the sake of brevity description, one exemplary embodiment has apattern of holes wherein each hole in the second array of holes alignslongitudinally with at least one other of the holes of the second arrayof holes and also aligns laterally with at least one differing hole ofthe second array of holes. But, the holes aligned longitudinally in thefirst array of holes do not align longitudinally with the holes alignedlongitudinally in the second array of holes. This misalignment willcause the inflation gas to be redirected after passing through the firstarray of holes of the inner layer portion.

The outer layer portion comprises a third array of holes arranged in athird grid. The third grid may be identical to the first grid, but neednot be so. An exemplary embodiment of the third grid has a pattern ofholes wherein each hole in the third array of holes alignslongitudinally with at least one other of the holes of the third arrayof holes and also aligns laterally with at least one differing hole ofthe third array of holes. But, the holes aligned longitudinally in thethird array of holes do not align longitudinally with the holes alignedlongitudinally in the second array of holes. Again, this misalignmentwill cause the inflation gas to be redirected after passing through thesecond array of holes of the intermediate layer portion.

The unitary body (as pre-prepped, see description above) in the insertedspiral rolled mode may be formed by wrapping the unitary body around acorrectly-sized mandrel or by other suitable means. As wrapped, thefilter module does not need to be welded to hold its shape once insertedinto the inflator. As inserted, the filter module is coaxial with thecentral longitudinal axis of the housing of the inflator in a rolled,spiraling fashion. When disposed within the housing, the filter modulecomprised of the spiraling unitary body has a configuration such thatthe inner layer portion defines an inner layer, the intermediate layerportion defines an intermediate layer, and the outer layer portiondefines an outer layer.

In one exemplary embodiment, the first array of holes of the inner layerportion surround the central longitudinal axis such that thelongitudinally aligned holes of the first array of holes define a firstset of planes each substantially perpendicular to the centrallongitudinal axis. This occurs because the unitary body has been rolledabout a lateral axis and then placed within the inflator so that thelateral axis of the rolled unitary body aligns with the centrallongitudinal axis of the inflator housing, or is at least parallel andclosely proximate to the central longitudinal axis. Consequently, thelaterally aligned holes of the first array of holes define a first setof axes substantially parallel to the central longitudinal axis. Theinner layer is positioned such that the gas passes through the firstarray of holes to reach the intermediate layer.

Similarly, the second array of holes of the intermediate layer portionsurrounds the inner layer and the central longitudinal axis. Hence, thelongitudinally aligned holes of the second array of holes define asecond set of planes each substantially perpendicular to the centrallongitudinal axis and each offset from the first set of planes. Thelaterally aligned holes of the second array of holes define a second setof axes substantially parallel to the central longitudinal axis. Theintermediate layer is positioned such that the gas passes through thesecond array of holes to reach the outer layer.

The third array of holes of the outer layer surrounds the inner layer,the intermediate layer, and the central longitudinal axis. Thelongitudinally aligned holes of the third array of holes define a thirdset of planes each substantially perpendicular to the centrallongitudinal axis and each offset from the second set of planes. Thelaterally aligned holes of the third array of holes define a third setof axes substantially parallel to the central longitudinal axis. Theouter layer is positioned such that the inflation gas passes through thethird array of holes to reach the interior wall of the housing and atleast one diffuser hole.

As disclosed herein, the intermediate layer comprises a second array ofholes, each hole of the second array of holes is not aligned with thehole of the first array of holes nearest such hole of the second arrayof holes. Hence, the intermediate layer is positioned such that theinflation gas is redirected to move axially before the inflation gaspasses through the second array of holes to reach the outer layer. Theouter layer comprises a third array of holes, each hole of the thirdarray of holes is not aligned with the hole of the second array of holesnearest such hole of the third array of holes. Again the outer layer ispositioned such that the inflation gas is redirected to move axiallybefore the inflation gas passes through the third array of holes toreach the at least one diffuser hole of the housing.

Each exemplary embodiment of the filter module has a plurality ofprotrusions. These protrusions are disposed such that the inner layerportion (and therefore the inner layer) has at least one protrusion, theintermediate layer portion (and therefore the inner layer) has at leastone protrusion, and the outer layer portion (and therefore the outerlayer) has at least one protrusion. Each protrusion disposed on theinner layer portion is adjacent at least one of the holes of the firstarray of holes of the inner layer. Each protrusion disposed on theintermediate layer portion is adjacent at least one of the holes of thesecond array of holes of the intermediate layer. Each protrusiondisposed on the outer layer portion is adjacent at least one of theholes of the third array of holes of the outer layer. Such protrusionsmaintain a gap between the inner layer and the intermediate layer,between the intermediate layer and the outer layer, and between theouter layer and the exterior wall to define a spiraling plenum throughwhich the inflation gas passes on a tortuous path from the gas sourcethrough the filter module to exit through at least one diffuser hole inthe inflator.

In another exemplary embodiment of the unitary filter module of thepresent disclosure, the holes may be arranged in a staggered pattern.This staggered pattern may be incorporated into the first array of holesin the inner layer, the second array of holes in the intermediate layer,and/or the third array of holes in the outer layer. One example of astaggered pattern has multiple lines of longitudinally aligned holes andeach hole of any of the multiple lines of longitudinally aligned holesaligns laterally with at least one hole of another of the multiple linesof longitudinally aligned holes, but does not align laterally with anyof the holes of at least one other of the multiple lines oflongitudinally aligned holes.

These and other features and advantages of the exemplary embodiments ofthe present disclosure will become more fully apparent from thefollowing detailed description and appended claims, or may be learned bythe practice of the invention as set forth herein.

REFERENCE NUMBERS

filter module 10 unitary body 12 length L longitudinal direction 14width W lateral direction 16 inner layer portion 18 intermediate layerportion 20 outer layer portion 22 first array of holes 24 first grid 26holes (within the first array) 28 second array of holes 30 second grid32 holes (within the second array) 34 third array of holes 36 third grid38 holes (within the third array) 40 protrusions 42 longitudinal line 43inflator 44 longitudinal line 45 central longitudinal axis A housing 46lateral line 47 inner layer 48 lateral line 49 intermediate layer 50dimples 51 outer layer 52 elongated dimples 53 first set of planes P₁first set of axes L₁ inflation gas G third set of planes P₃ third set ofaxes L₃ interior wall 54 inclined flaps 55 diffuser hole 56 gap 58spiraling plenum 60 flow (arrows) 61 gas source 62 staggered pattern 64space 66 inner diameter (outer layer) 68 inner diameter (inner layer) 70burst disk 72

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will become more fully apparentfrom the following description and appended claims, taken in conjunctionwith the accompanying drawings. Understanding that these drawings depictonly exemplary embodiments and are, therefore, not to be consideredlimiting of the invention's scope, the exemplary embodiments of theinvention will be described with additional specificity and detailthrough use of the accompanying drawings in which:

FIG. 1 is a perspective view of an exemplary embodiment of a unitarybody for a filter module in the flat mode showing protrusions adjacentholes;

FIG. 2 is a plan view of the exemplary unitary body of FIG. 1 in a flatmode;

FIG. 3 is a perspective view of the exemplary unitary body of FIG. 1 ina spiral rolled mode;

FIG. 4 is partial, section view of an inflator having a filter moduleinserted therein and showing exemplary inflation gas flow paths;

FIG. 5 is a plan view of the exemplary unitary body in a flat mode andshowing exemplary longitudinal and lateral lines;

FIG. 6 is a plan view of an alternative exemplary unitary body in a flatmode and showing exemplary staggered lateral lines;

FIG. 7 is a plan view of another exemplary unitary body in a flat modeand showing exemplary laterally elongated protrusions arranged instaggered lateral lines;

FIG. 8 is a longitudinal section view of the unitary body of FIG. 7 in aspiral rolled mode showing a spiral plenum

FIG. 9 is a plan view of yet another exemplary unitary body in a flatmode and showing an example of differing hole sizes;

FIG. 10 is partial, section view of an inflator having a filter moduledisposed within the inflator housing in an inserted, spiral rolled mode;

FIG. 11 is partial, section view of an inflator having a filter moduledisposed within the inflator housing in an inserted, spiral rolled modesimilar to FIG. 10, except having a filter module with a greater widthso to create a larger diameter for burst disk rupture; and

FIG. 12 is partial, section view of an inflator having an alternativeexemplary filter module disposed within the inflator housing in aninserted, spiral rolled mode, wherein each hole forms an inclined flapthat serves as a protrusion.

DETAILED DESCRIPTION

Exemplary embodiments of the present invention will be best understoodby reference to the drawings, wherein like parts are designated by likenumerals throughout. It will be readily understood that the componentsof the present invention, as generally described and illustrated in theFigures herein, could be arranged and designed in a wide variety ofdifferent configurations. Thus, the following more detailed descriptionof exemplary embodiments of the apparatus, system, and method of thepresent invention, as represented in FIGS. 1 through 4, is not intendedto limit the scope of the invention, as claimed, but is merelyrepresentative of exemplary embodiments of the invention.

The phrases “connected to,” “coupled to” and “in communication with”refer to any form of interaction between two or more entities, includingmechanical, electrical, magnetic, electromagnetic, fluid, and thermalinteraction. Two components may be coupled to each other even thoughthey are not in direct contact with each other. The term “abutting”refers to items that are in direct physical contact with each other,although the items may not necessarily be attached together. The phrase“fluid communication” refers to two features that are connected suchthat a fluid that exits one feature is able to pass into or otherwisecontact the other feature.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any embodiment described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments. While the various aspects of theembodiments are presented in drawings, the drawings are not necessarilydrawn to scale unless specifically indicated.

The word “unitary” is used herein to mean a single unit. Such singleunit may be made from one piece of material, but need not be so. Morethan one piece of material can be formed into a single unit. So long asan article functions as a single unit, that article is considered to be“unitary.”

Inflatable airbag systems are widely used to minimize occupant injury ina collision scenario. Airbag modules have been installed at variouslocations within a vehicle, including, but not limited to, the steeringwheel, the instrument panel, within the side doors or side seats,adjacent to the roof rail of the vehicle, in an overhead position, or atthe knee or leg position. In the following disclosure, “airbag” mayrefer to any airbag type.

Referring to FIGS. 1, 2 and 5, an exemplary embodiment of a unitary body12 for a filter module 10 is shown in the flat mode. The unitary body 12has a length L (a longitudinal direction 14) and a width W (a lateraldirection 16) and is generally divided into an inner layer portion 18,an intermediate layer portion 20, and an outer layer portion 22.

In the flat mode, the inner layer portion 18 is prepared with a firstarray of holes 24 arranged in a first grid 26. This first grid 26 mayhave any of a number of patterns, but one exemplary pattern of holes arearranged such that each hole 28 in the first array of holes 24 alignslongitudinally with at least one other of the holes of the first arrayof holes 24 and also aligns laterally with at least one differing holeof the first array of holes 24. The intermediate layer portion 20comprises a second array of holes 30 arranged in a second grid 32. Thesecond grid 32 need not have the same number, pattern, or size of holesas the first array of holes 24.

Although exemplary embodiments are disclosed herein, for the sake ofbrevity in the description, not all possible arrays will be disclosedherein. Those skilled in the art, armed with this disclosure, mayfashion and prepare many different arrays of holes that will not departfrom the spirit of this disclosure. Also, for the sake of brevity and sonot to obscure the features being disclosed a single intermediate layerportion 20 is shown throughout the drawings. It should be understood,however, that there may be more than one intermediate layer portion 20and that intermediate layers need not necessarily have the same array ofholes.

One exemplary embodiment, shown in FIG. 5, has a pattern of holeswherein each hole 34 in the second array of holes 30 alignslongitudinally with at least one other of the holes 34 of the secondarray of holes 30 and also aligns laterally with at least one differinghole 34 of the second array of holes 30. But, the holes 28 alignedlongitudinally in the first array of holes 24 do not alignlongitudinally with the holes 34 aligned longitudinally in the secondarray of holes 30. This misalignment will cause the inflation gas to beredirected after passing through the first array of holes 24 of theinner layer portion 18.

The outer layer portion 22 comprises a third array of holes 36 arrangedin a third grid 38. The third grid 38 may be identical to the first grid26, but need not be so. An exemplary embodiment of the third grid 38 hasa pattern of holes wherein each hole 40 in the third array of holes 36aligns longitudinally with at least one other of the holes 40 of thethird array of holes 36 and also aligns laterally with at least onediffering hole 40 of the third array of holes 36. But, the holes 40aligned longitudinally in the third array of holes 36 do not alignlongitudinally with the holes 34 aligned longitudinally in the secondarray of holes 34. Again, this misalignment will cause the inflation gasto be redirected after passing through the second array of holes 34 ofthe intermediate layer portion 20.

Each exemplary embodiment of the filter module 10 has a plurality ofprotrusions 42. These protrusions 42 are disposed such that the innerlayer portion 18 has at least one protrusion 42 and likely several, theintermediate layer portion 20 has at least one protrusion 42 and likelyseveral, and the outer layer portion 22 has at least one protrusion 42and likely several. Each protrusion 42 disposed on the inner layerportion 18 is adjacent at least one of the holes 28 of the first arrayof holes 24 of the inner layer portion 18. Each protrusion 42 disposedon the intermediate layer portion 20 is adjacent at least one of theholes 34 of the second array of holes 30 of the intermediate layerportion 20. Each protrusion 42 disposed on the outer layer portion 22 isadjacent at least one of the holes 40 of the third array of holes 36 ofthe outer layer portion 22. Such protrusions 42 are designed and locatedto maintain a gap (not shown in FIGS. 1, 2 and 5, see FIGS. 3, 4, 8, 10and 11) between the inner layer and the intermediate layer, between theintermediate layer and the outer layer, and between the outer layer andthe exterior wall to define a spiraling plenum through which theinflation gas passes on a tortuous path from the gas source through thefilter module to exit through at least one diffuser hole in the inflator44.

With the exemplary embodiment shown in FIG. 5, each protrusion 42 alignslongitudinally with at least one other protrusion 42 along alongitudinal line. Such longitudinal line within the second array ofholes 30 passes through holes 34 and protrusions and is shown aslongitudinal line 43. Another such longitudinal line within the thirdarray of holes 36 passes through holes 40 and protrusions 42 and isshown as longitudinal line 45. The longitudinal lines of the secondarray of holes 30, of which longitudinal line 43 is one, do not alignwith any of the longitudinal lines of the first array of holes 24 or thethird array of holes 36, of which longitudinal line 45 is one.

Similarly, in FIG. 5, each protrusion 42 aligns laterally with at leastone other protrusion 42. Such a lateral line is shown within theintermediate portion 20 as lateral line 47, and another lateral line isshown within the outer layer portion 22 as lateral line 49. This lateralalignment, in cooperation with the longitudinal misalignment of holes28, 34, 40 virtually assures that holes 28, 34, 40 will not align fromlayer to layer of the filter module 10. As a result, the flow ofinflation gas through the filter module 10 will necessarily travel atortuous path.

Again, it should be understood that the protrusions 42 can take on manyforms in many sizes and shapes without departing from the spirit of thisdisclosure. For example, the protrusions 42 may be dimples 51 (see FIGS.5 and 6) that form a mound but do not perforate the unitary body 12 ofthe filter module 10, elongated dimples 53 (see FIGS. 7 and 9), ridges,or inclined flaps 55 (see FIG. 12) made by piercing the unitary body 12(forming holes in the form of slits) and bending the flaps 55 on anincline to reach a desired height. So long as the number of protrusions42 are of sufficient number, size and height and dispersed sufficientlyto maintain the gap 58 that defines the spiral plenum 60, protrusions 42serve their function while strengthening the layers, 48, 50, 52 of thefilter module 10. Of course, having more protrusions 42 will dictatethat the flow of inflation gas that must move around such protrusions 42will take more tortuous paths to exit the inflator 44; however, thenumber, size, and distribution of the protrusions 42 and the holes 28,34, 40 may be adjusted and may be fine-tuned to optimize the desiredamount of flow restriction, the desired amount of cooling, and/or thedesired amount of impurities capture for the filling of an airbag in themost material-effective and cost-effective way. Since the desired amountof flow restriction, the desired amount of cooling, and/or the desiredamount of impurities capture for the filling an airbag is dependent uponthe size, shape, location, and the desired rate of deployment of theairbag, the number, size, and distribution of the protrusions 42 and theholes 28, 34, 40 should be adjusted and fine-tuned to optimize theeffectiveness of the filter module 10 used in each type of inflator.

The unitary body 12, as pre-prepped (see FIGS. 1, 2 and 5), may betransformed into the inserted spiral rolled mode by wrapping the unitarybody 12 around a correctly-sized mandrel (not shown) or by any othersuitable means. Before insertion into the inflator 44 and after formingunitary body 12 into a rolled spiral of a generally tubular shape, thefilter module 10 appears as shown in FIG. 3. As rolled, the filtermodule 10 does not need to be welded to hold its shape once insertedinto an inflator 44. As inserted, the filter module 10 is coaxial with acentral longitudinal axis A of a housing 46 of the inflator 44 in arolled, spiraling fashion as shown in FIG. 4. When disposed within thehousing 46, the filter module 10 has a spiraling unitary body 12 with aconfiguration such that the inner layer portion 18 defines an innerlayer 48, the intermediate layer portion 20 defines an intermediatelayer 50, and the outer layer portion 22 defines an outer layer 52, asshown in FIGS. 3 and 4.

Again, for the sake of brevity and so not to obscure the features beingdisclosed a single intermediate layer portion 20 and a singleintermediate layer 50 are shown throughout the drawings. It should beunderstood, however, that there may be more than one intermediate layerportion 20, more than one intermediate layer 50 and that theintermediate layers 50 need not necessarily have the same array ofholes.

In one exemplary embodiment, the first array of holes 24 of the innerlayer portion 18 surround the central longitudinal axis A such that thelongitudinally aligned holes 28 of the first array of holes 24 define afirst set of planes P₁ each substantially perpendicular to the centrallongitudinal axis A (see e.g., FIGS. 4 and 8). This occurs because theunitary body 12 has been rolled about a lateral axis and then placedwithin the inflator so that the lateral axis of the rolled unitary bodyaligns with the central longitudinal axis A of the inflator housing 46,or is at least parallel and closely proximate to the centrallongitudinal axis A. Consequently, the laterally aligned holes 28 of thefirst array of holes 24 define a first set of axes Li substantiallyparallel to the central longitudinal axis A (see e.g., FIGS. 4 and 8).The inner layer 48 is positioned such that the inflation gas G passesthrough the first array of holes 24 to reach the intermediate layer 50.

Similarly, the second array of holes 30 of the intermediate layerportion 20 surrounds the inner layer 48 and the central longitudinalaxis A. Hence, the longitudinally aligned holes 34 of the second arrayof holes 30 define a second set of planes P₂ each substantiallyperpendicular to the central longitudinal axis A and each offset fromthe first set of planes P₁. The laterally aligned holes 34 of the secondarray of holes 30 define a second set of axes L₂ substantially parallelto the central longitudinal axis A. The intermediate layer 50 ispositioned such that the inflation gas G passes through the second arrayof holes 30 to reach the outer layer 52.

The third array of holes 36 of the outer layer 52 surrounds the innerlayer 48, the intermediate layer 50, and the central longitudinal axisA. The longitudinally aligned holes 40 of the third array of holes 36define a third set of planes P₃ each substantially perpendicular to thecentral longitudinal axis A and each offset from the second set ofplanes P₂. The laterally aligned holes 40 of the third array of holes 36define a third set of axes L₃ substantially parallel to the centrallongitudinal axis A. The outer layer 52 is positioned such that theinflation gas G passes through the third array of holes 36 to reach aninterior wall 54 of the housing 46 and at least one diffuser hole 56.

As disclosed in at least one exemplary embodiment herein (best shown inFIG. 4), the intermediate layer 50 comprises a second array of holes 30,each hole 34 of the second array of holes 30 is not aligned with thehole 28 of the first array of holes 24 nearest such hole 34 of thesecond array of holes 30. Hence, the intermediate layer 50 is positionedsuch that the inflation gas G is redirected to move axially before theinflation gas G passes through the second array of holes 30 to reach theouter layer 52. The outer layer 54 comprises a third array of holes 36,each hole 40 of the third array of holes 36 is not aligned with the hole34 of the second array of holes 30 nearest such hole 40 of the thirdarray of holes 54. Again, the outer layer 52 is positioned such that theinflation gas G is redirected to move axially before the inflation gas Gpasses through the third array of holes 36 to reach the at least onediffuser hole 56 of the housing 46.

Each exemplary embodiment of the filter module 10 has a plurality ofprotrusions 42. These protrusions 42 are disposed such that the innerlayer portion 18 (and therefore the inner layer 48) has at least oneprotrusion 42, the intermediate layer portion 20 (and therefore theintermediate layer 50) has at least one protrusion 42, and the outerlayer portion 22 (and therefore the outer layer 52) has at least oneprotrusion 42. Each protrusion 42 disposed on the inner layer portion 18is adjacent at least one of the holes 28 of the first array of holes 24of the inner layer 48. Each protrusion 42 disposed on the intermediatelayer portion 20 is adjacent at least one of the holes 34 of the secondarray of holes 30 of the intermediate layer 50. Each protrusion 42disposed on the outer layer portion 22 is adjacent at least one of theholes 40 of the third array of holes 36 of the outer layer 52. Suchprotrusions maintain a gap 58 between the inner layer 48 and theintermediate layer 50, between the intermediate layer 50 and the outerlayer 52, and between the outer layer 52 and the interior wall 54 ofhousing 46 to define a spiraling plenum 60 through which the inflationgas G passes on a tortuous path (best understood by following flowarrows 61 shown in FIGS. 4 and 12) from the gas source 62 through thefilter module 10 to exit through at least one diffuser hole 46 in theinflator 46.

So long as the number of protrusions 42 are of sufficient number, sizeand height and dispersed sufficiently to maintain the gap 58 thatdefines the spiral plenum 60, protrusions 42 serve their function whilestrengthening the layers 48, 50, 52 of the filter module 10. Of course,having more protrusions will dictate that the flow of inflation gas Gthat must move around such protrusions 42 take more tortuous paths toexit the inflator 44. However, the number, size, and distribution of theprotrusions 42 and the holes 28, 34, 40 may be adjusted and may befine-tuned to optimize the desired amount of flow restriction, thedesired amount of cooling, and/or the desired amount of impuritiescapture for the filling of an airbag in the most material-effective andcost-effective way. Since the desired amount of flow restriction, thedesired amount of cooling, and/or the desired amount of impuritiescapture for the filling an airbag is dependent upon the size, shape,location, and the desired rate of deployment for the airbag, the number,size, and distribution of the protrusions 42 and the holes 28, 34, 40should be adjusted and fine-tuned to optimize the effectiveness of thefilter module 10.

In some embodiments, such as is shown in FIG. 9, the holes 28 of thefirst array of holes 24 in the inner layer 48 are each larger than theholes 34 of the second array of holes 30 in the intermediate layer 50.By enlarging the holes 28 in the first array of holes 24 in the innerlayer 48, unwanted erosion of the intermediate layer 50 due to the flow61 of hot inflation gas G jetting straight through the holes 28 of thefirst array of holes 24 against the inside wall of the intermediatelayer 50 can be mitigated. The size of the holes 28 of the first arrayof holes 24 may be enlarged until erosion is no longer observed.Similarly, the holes 34 of the second array of holes 30 can also beenlarged to avoid erosion on the outer layer 52 of the filter module 10.

Additionally, a desired choking point in the flow 61 of inflation gas Gthrough the inflator 44 may be determined by adjusting the number and/orsize of the holes 28, 34, 40 in the first array of holes 24, in thesecond array of holes 30, and in the third array of holes 36, as well asthe number and/or size of the diffuser holes 56.

In another exemplary embodiment of the unitary filter module 10 of thepresent disclosure, as shown in FIGS. 6, 7, and 9, the holes 28, 34, 40and protrusions 42 may be arranged in a staggered pattern 64. Thisstaggered pattern 64 may be incorporated into the first array of holes24 in the inner layer 48, the second array of holes 30 in theintermediate layer 50, and/or the third array of holes 36 in the outerlayer 52. One example of a staggered pattern 64 has multiple lines oflongitudinally aligned holes and each hole of any of the multiple linesof longitudinally aligned holes aligns laterally with at least one holeof another of the multiple lines of longitudinally aligned holes, butdoes not align laterally with any of the holes of at least one other ofthe multiple lines of longitudinally aligned holes.

In some embodiments, such as shown in FIG. 11, the unitary body 12 ofthe filter module 10 is wider at the outer layer 52 than at the innerand intermediate layers 48, 50. (FIG. 10 is provided for contrast,wherein the width of each layer 48, 50, 52 are the same.) When wrappedinto a spiral, the outer layer 52 is longer at one end than the innerand intermediate layers 48, 50. More space 66 is provided at that endbecause the inner diameter 68 of the outer layer 52 is larger than theinner diameter 70 of the inner layer 48. For inflators 44 with frangibleburst disks 72 disposed between the gas source 62 and the filter module10, the burst disk 72 has a larger diameter opening capability than itwould have had if the inner layer 48 abutted the burst disk 72. Thiswider configuration for the outer layer 52 enables the burst disk 72 toopen over the full, inner diameter 68 of the outer layer 52.

Any methods disclosed herein comprise one or more steps or actions forperforming the described method. The method steps and/or actions may beinterchanged with one another. In other words, unless a specific orderof steps or actions is required for proper operation of the embodiment,the order and/or use of specific steps and/or actions may be modified.

Reference throughout this specification to “an embodiment” or “theembodiment” means that a particular feature, structure or characteristicdescribed in connection with that embodiment is included in at least oneembodiment. Thus, the quoted phrases, or variations thereof, as recitedthroughout this specification are not necessarily all referring to thesame embodiment.

Similarly, it should be appreciated that in the above description ofembodiments, various features are sometimes grouped together in a singleembodiment, Figure, or description thereof for the purpose ofstreamlining the disclosure. This method of disclosure, however, is notto be interpreted as reflecting an intention that any claim require morefeatures than those expressly recited in that claim. Rather, as thefollowing claims reflect, inventive aspects lie in a combination offewer than all features of any single foregoing disclosed embodiment.Thus, the claims following this Detailed Description are herebyexpressly incorporated into this Detailed Description, with each claimstanding on its own as a separate embodiment. This disclosure includesall permutations of the independent claims with their dependent claims.

Recitation in the claims of the term “first” with respect to a featureor element does not necessarily imply the existence of a second oradditional such feature or element. Elements recited inmeans-plus-function format are intended to be construed in accordancewith 35 U.S.C. § 112 Para. 6. It will be apparent to those having skillin the art that changes may be made to the details of theabove-described embodiments without departing from the underlyingprinciples of the invention.

While specific embodiments and applications of the present inventionhave been illustrated and described, it is to be understood that theinvention is not limited to the precise configuration and componentsdisclosed herein. Various modifications, changes, and variations whichwill be apparent to those skilled in the art may be made in thearrangement, operation, and details of the methods and systems of thepresent invention disclosed herein without departing from the spirit andscope of the invention.

What is claimed is:
 1. A unitary filter module for insertion into aninflator for an airbag assembly, the inflator having a gas source, theunitary filter module having a flat mode and an inserted spiral rolledmode and comprising: a unitary body having a length, a width, an innerlayer portion, an intermediate layer portion, and an outer layer portionin the flat mode: the inner layer portion comprises a first array ofholes; the intermediate layer portion comprises a second array of holes;a plurality of protrusions; and wherein at least one of the first arrayof holes and the second array of holes has a staggered array patternwherein the staggered array pattern comprises multiple lines oflongitudinally aligned holes and each hole of any of the multiple linesof longitudinally aligned holes aligns laterally with at least one holeof another of the multiple lines of longitudinally aligned holes butdoes not align laterally with any of the holes of at least one other ofthe multiple lines of longitudinally aligned holes; the unitary body inthe inserted spiral rolled mode is rolled around a central longitudinalaxis into a spiral, each protrusion maintaining a gap between the innerlayer portion and the intermediate layer portion; and wherein theunitary body of the filter module is wider at the outer layer portionthan at the inner layer portion and intermediate layer portion, and theinflator has a frangible burst disk between the gas source and theunitary filter module thereby enabling the burst disk to open over thefull diameter of the outer layer portion.
 2. The filter module of claim1, wherein the protrusions are dimples.
 3. The filter module of claim 2,wherein each dimple is elongate.
 4. The filter module of claim 1,wherein at least one of the size, shape, number, location, anddistribution of the holes and protrusions are adjustable to enable theeffectiveness of the filter module to be fine-tuned.